Slice the onions into 1/2-inch wide rings then place the rings in a bowl of water.

In a medium bowl, whisk together the flour, 1 teaspoon salt and 1/4 teaspoon pepper. In a second medium bowl, whisk together the egg whites and the mayonnaise. Add the breadcrumbs to a third medium bowl. Remove each onion ring from the water, shaking off any excess and then placing it immediately into the flour, tossing until it’s thoroughly coated. Next, dip the onion ring into the egg white mixture until it’s thoroughly coated and then into the breadcrumbs, pressing them firmly onto all sides of the onion ring. Place the onion ring on the prepared baking sheet and repeat the coating process with the remaining onion rings.

Throughly spray the onion rings with cooking spray (optional, but it helps them brown more evenly). Bake the onion rings for 10 minutes then flip them once and bake an additional 5 minutes until they’re golden brown and crispy. Serve immediately with your favorite dipping sauce.